virtual private network

virtual private network

[¦vər·chə·wəl ‚prī·vət ′net‚wərk]

(communications)

A wide-area network whose links are provided by a common carrier although they appear to the users to behave like dedicated lines, and whose computers use a common cryptographic key to send messages from one computer in the network to another. Abbreviated VPN.

Virtual Private Network

(networking, security)

(VPN) The use of encryption in the
lower protocol layers to provide a secure connection through
an otherwise insecure network, typically the Internet. VPNs
are generally cheaper than real private networks using private
lines but rely on having the same encryption system at both
ends. The encryption may be performed by firewall software
or possibly by routers.

Link-level (layer 2 and 3) encryption provides extra
protection by encrypting all of each datagram except the
link-level information. This prevents a listener from
obtaining information about network structure. While
link-level encryption prevents traffic analysis (a form of
attack), it must encrypt/decrypt on every hop and every
path.

Protocol-level encryption (layer 3 and 4) encryption encrypts
protocol data but leaves protocol and link headers clear.
While protocol-level encryption requires you to
encrypt/decrypt data only once, and it encrypts/decrypts only
those sessions that need it, headers are sent as clear text,
allowing traffic analysis.

Application (layer 5 up) encryption is based on a particular
application and requires that the application be modified to
incorporate encryption.

Cisco.

virtual private network

A private network configured within a public network such as the Internet or a carrier's network. Years ago, virtual private networks (VPNs) obsoleted private lines between company branches. Using data encryption to maintain privacy, VPNs also allow mobile users access to the company LAN.

In the past, common carriers used their vast networks to "tunnel" traffic between customer locations to give the appearance of a private network while sharing backbone trunks, no different than the way the Internet works. Prior to the Internet's IP protocol, VPNs were built over X.25, Switched 56, frame relay and ATM technologies. See PVC, SVC, computer security and information security.

Internet VPNs Internet VPNs are very popular, and several security protocols are used. IPsec, L2TP and PPTP provide secure tunnels over the Internet. For brief transactions at a website, SSL is widely used. See IPsec, L2TP, PPTP and SSL.

Ethernet VPNs from Carriers Carriers encapsulate Ethernet frames in one location and deliver them to another. Connecting two Ethernets is a "LAN interconnect service," while multipoint connectivity is a "transparent LAN service" (TLS). A "virtual private LAN service" (VPLS) is a multipoint VPN using an IP/MPLS core to route traffic. See TLS, VPLS and IP/MPLS core.

Frame Relay VPNs from Carriers Carriers have offered frame relay point-to-point and multipoint VPNs, whereby the customer's equipment converts internal IP packets to frame relay packets. Adding a location in such a network means provisioning virtual circuits from the new site to all the other sites. See frame relay.

Blue Ridge Networks, a leading provider of outsourced Virtual Private Networking (VPN) solutions, and AB&T Telecom, a leading provider of communication products and services, today announced a partnership that will provide Blue Ridge Network's VPN technology to AB&T's extensive list of telecommunication service resellers.

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